Splitting reset into pre and post reset.

src/update.py

@@ -7,18 +7,28 @@ class Update:
         self.view = None
 
     def update_model(self):
-        # any update resets menu_location, except if it explicitly defines it
+        # check if we need to reset the model
+        reset = False
         for msg in self.message_queue:
             if msg.reset():
-                self.model.reset()
+                reset = True
                 break
+        
+        if reset:
+            self.model.pre_reset()
             
+        # check if we need to signal the data change
         for msg in self.message_queue:
             if msg.data_change():
                 screenful.changed()
-        
+                break
+            
+        # do update
         for msg in self.message_queue:
             msg.update_model(self.model)
+            
+        if reset:
+            self.model.post_reset()
 
         self.message_queue = []
         self.view.view(self.model)